Systems and methods for protecting a trunk with multiple trunks

ABSTRACT

A system and method for protecting a trunk with multiple trunks may select a primary path on a first trunk for which to place a corresponding bypass tunnel on a second trunk. The system and method may further select one or more alternate trunks using a constraint-based trunk-selection algorithm. The system and method may further determine if at least one of the selected alternate trunks has sufficient priority bandwidth. In the event that one or more alternate trunks have priority bandwidths larger than the physical bandwidth of the primary path, the system and method may select an alternate trunk from the one or more alternate trunks having priority bandwidths larger than the physical bandwidth of the primary path based on a pre-determined order of priority bandwidth.

BACKGROUND INFORMATION

A network may deliver packets via a connectionless protocol, e.g.,Internet Protocol (IP), and/or a connection oriented protocol, e.g.,Multiprotocol Label Switching protocol (MPLS). Connection orientedprotocols may pre-calculate a path between a source node and adestination node, and deliver packets on the path. The path may bereferred to as a “primary path.” The establishment of primary paths maytake into consideration factors such as, but not limited to, prioritiesof paths, and network available bandwidth. In the event a link or nodeon a primary path fails, data traffic carried on the primary path mustbe re-routed to an alternate path within a specified time using alink/node protection, e.g., a fast re-route (FRR). As a network addsmore capacity and carries more data traffic, the network may carryuneven data traffic loads among different trunks and nodes. Existinglink/node protection may not optimize the alternate path building tobalance the data traffic loads.

BRIEF DESCRIPTION OF THE DRAWINGS

Purposes and advantages of the exemplary embodiments will be apparent tothose of ordinary skill in the art from the following detaileddescription in conjunction with the appended drawings in which likereference characters are used to indicate like elements, and in which:

FIG. 1 is a block diagram of a network node with four network interfacesaccording to an exemplary embodiment;

FIG. 2 is a schematic diagram of a trunk protected by multiple Next Hoptrunks according to an exemplary embodiment;

FIG. 3 is a schematic diagram of a link/node protected by multiple NextNext Hop trunks according to an exemplary embodiment; and

FIG. 4 is a flow diagram of a method to implement link/node protectionaccording to an exemplary embodiment.

These and other embodiments and advantages will become apparent from thefollowing detailed description, taken in conjunction with theaccompanying drawings, illustrating by way of example the principles ofthe various exemplary embodiments.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

For connection oriented networks, pre-determined alternate paths areused to protect against connection failures. Failure protection mayrequire a fast re-route of a failed primary path to an alternate pathcarried on a different physical link. The fast re-route may require alimited response time, e.g., fifty milliseconds (50 ms). The physicallinks carrying the primary path and the alternate path may be referredto as “trunks.” The alternate path may be referred to as a “bypasstunnel.”

Various types of data may be transmitted between nodes in a datacommunication network. A primary path carrying a certain type or typesof data may have a specific setup priority and a specific holdingpriority. The setup priority and holding priority determine whichprimary path may be established on the network if the network is runninglow on resources (e.g., bandwidth), or alternately, which existingprimary path may be preempted from the network. Holding priorities maybe used to rank existing primary paths, and setup priorities may be usedto determine if a new primary path can preempt an existing primary path.The setup priority and holding priority may be assigned a value in arange, e.g., zero (0, lowest) to seven (7, highest). The setup priorityand holding priority may define the relative importance of the datatraffic. A primary path with a higher setup priority may preempt anexisting primary path with a lower holding priority. A primary path mayhave the same value for the primary path's setup priority and holdingpriority (e.g., a setup priority of seven (7) and a holding priority ofseven (7)) or different values (e.g., a setup priority of six (6) and aholding priority of five (5)). Thus, when primary paths are beingestablished, a primary path with a setup priority of six (6), forexample, has a higher priority of being set up than all other primarypaths having priorities lower than six (6). Also, the same primary pathmay preempt existing primary paths having holding priorities of five (5)or lower if there is not enough network bandwidth to accommodate theprimary path. When bypass tunnels are established for primary paths, thebypass tunnels may have the same setup priority and holding priority asthe corresponding primary paths.

As is well known, network circuits may be overbooked (also known asoversubscribed) using an overbooking factor. Overbooking of a networkmay also be referred to as oversubscription of a network, and theoverbooking factor may be referred to as an oversubscription factor. Inthis disclosure, the term “overbooking factor” may be interchangeablewith “oversubscription factor.”

There may be at least three different kinds of overbooking factors. Oneis for trunks, another is for primary paths, and the third is for bypasstunnels. It is well known that a trunk may be overbooked so that thetrunk may provide more bandwidth to subscribers than physicallyavailable. The bandwidth provided by the trunk may be referred to as aprovisioned bandwidth of the trunk. The provisioned bandwidth of thetrunk may also be referred to as a logical bandwidth of the trunk. Forexample, a trunk may have a physical bandwidth of one Gbps (1 Gigabitsper second). If the trunk's overbooking is two-to-one (2:1), e.g., anoverbooking factor of two-hundred percent (200%), then the trunk mayprovide a two (2) Gbps logical bandwidth for all the primary paths orbypass tunnels carried by the trunk. That is, from a primary path'sperspective or a bypass tunnel's perspective, the trunk appears to havea physical bandwidth of two (2) Gbps. In the description below, thephysical bandwidth referred to is the physical bandwidth from theperspective of primary paths or bypass tunnels.

All primary paths carried on a trunk may be overbooked as well. That is,a primary path may have a physical bandwidth on the trunk but may offermore bandwidth to the data traffic carried on the primary path.Continuing the previous example, a primary path may have a physicalbandwidth of two hundred Mbps (200 Megabits per second) on the trunk andmay have an overbooking factor of two-hundred percent (200%). That is,the primary path offers four hundred (400) Gbps bandwidth to datatraffic carried by the primary path. The four hundred (400) Mbpsbandwidth may be referred to as a provisioned bandwidth of the primarypath. The provisioned bandwidth of the primary path may also be referredto as a logical bandwidth of the primary path.

When placing a bypass tunnel on a second trunk for a primary path, anetwork administrator may set a bypass overbooking factor. Because thebypass tunnel may be used to provide a backup of the primary path andmay not carry data traffic during normal operation of the network, thenetwork administrator may want to conserve bandwidth on the second trunkby setting a bypass tunnel overbooking factor less than one-hundredpercent (100%). Continuing the previous example, the bypass tunneloverbooking factor for the two hundred (200) Mbps primary path may beset to ten-percent (10%), so the primary path may appear to have atwenty (20) Mbps physical bandwidth for the second trunk where thebypass tunnel may be placed. All data traffic carried on the bypasstunnel may not be impacted, because the data traffic is still offeredthe logical bandwidth of the primary path, not the bypass tunnel'sbandwidth. That is, the data traffic carried on the bypass tunnel maystill see that the bypass tunnel has a bandwidth of four hundred (400)Mbps.

As is well known, network link protection may be carried out by a NextHop protection scheme or a Next Next Hop protection scheme. In a NextHop protection scheme, a physical link between a first node and a secondnode may be protected by a different route from the first node to thesecond node. The different route may be referred to as a Next Hop trunk.Exemplary embodiments described herein may provide protection for aphysical link by applying a Next Hop protection scheme. In a Next NextHop protection scheme, a physical link between a first node and a secondnode, and the second node itself, may both be protected by a differentroute from the first node to a third node immediately downstream fromthe second node. The different route may be referred to as a Next NextHop trunk. Exemplary embodiments described herein may further provideprotection for a link/node by applying a Next Next Hop protectionscheme.

Each Next Hop trunk or Next Next Hop trunk may have one or more existingprimary paths. A bypass tunnel may consider a “priority bandwidth” of aNext Hop trunk or Next Next Hop trunk to determine whether the Next Hoptrunk or Next Next Hop trunk may have enough bandwidth to accommodatethe bypass tunnel. As described previously, a bypass tunnel may alsohave a setup priority and a holding priority. A bypass tunnel with ahigher setup priority may preempt existing primary paths with lowerholding priorities. Therefore, for the bypass tunnel, physicalbandwidths allocated to existing primary paths with holding prioritiesequal to or higher than the bypass tunnel's setup priority are notavailable. The amount of physical bandwidth of a Next Hop trunk or NextNext Hop trunk that is available for a bypass tunnel may be referred toas a priority bandwidth, which is the total bandwidth of the trunk minusall of the physical bandwidths allocated to existing primary paths withequal or higher holding priority values. Physical bandwidth of anybypass tunnels that may be built on the Next Hot trunk or Next Next Hoptrunk are not considered in determining the priority bandwidth. Forexample, a Next Hop trunk may have a physical bandwidth of ten (10)Gbps. The Next Hop trunk may have two existing primary paths. The firstprimary path may have a logical bandwidth of four (4) Gbps, anoverbooking factor of four hundred (400%), a physical bandwidth of one(1) Gbps, a setup priority of seven (7) and a holding priority of five(5). The second primary path may have a logical bandwidth of ten (10)Gbps, an overbooking factor of one-thousand percent (1000%), a physicalbandwidth of one (1) Gbps, a setup priority of six (6) and a holdingpriority of six (6). For a bypass tunnel with a setup priority of seven(7), the priority bandwidth is ten (10) Gbps because there is noexisting primary path with a holding priority of seven (7) on the NextHop trunk 204. For a bypass tunnel with a setup priority of six (6), thepriority bandwidth is nine (9) Gbps because the second primary path hasa holding priority of six (6) and the second primary path's physicalbandwidth of one (1) Gbps is not available for the bypass tunnel. For abypass tunnel with a setup priority of five (5), the priority bandwidthis eight (8) Gbps because the first primary path has a holding priorityof five (5) and the second primary path has a holding priority of six(6). For the bypass tunnel, the priority bandwidth is ten (10) Gbpsminus one (1) Gbps for the first primary path, and minus one (1) Gbpsfor the second primary path. Therefore, for each bypass tunnel, a NextHop trunk or Next Next Hop trunk may have a different available physicalbandwidth depending on the setup priority of the bypass tunnel.

Exemplary embodiments described herein may provide link/node protection.Such link/node protection may set up bypass tunnels for each primarypath on a first trunk with the bypass tunnels being placed on one ormore trunks (e.g., alternate trunks) other than the first trunk. Thebypass tunnels are the result of a Next Hop or a Next Next Hopprotection scheme. Each primary path may build a corresponding bypasstunnel based on a pre-determined order of the setup priority andphysical bandwidth of the primary path. Each bypass tunnel may be placedusing a trunk selection scheme. The trunk selection scheme may startwith a constraint-based trunk-selection algorithm, compute a prioritybandwidth for each available Next Hop or Next Next Hop trunk, employ athreshold value for the priority bandwidth, conserve the bandwidth onthe alternate trunk by either setting a user defined value for areserved physical bandwidth for the bypass tunnel or applying a bypasstunnel overbooking factor to the physical bandwidth of the primary path,and perform preemption when necessary. Additionally, exemplary link/nodeprotection may associate all primary paths on the first trunk with theircorresponding bypass tunnels on the other trunks in a database andreroute all data traffic on the first trunk to the other trunks when afailure occurs for a primary path. Further, link/node protection may beapplied during primary path setup, periodically to optimize networkbypass tunnel design, and/or any time a network administrator maydecide.

The description below describes networks, network nodes and methodsimplemented by the networks or network nodes. It is noted that themethods may be implemented as software and software described herein maybe tangibly embodied in one or more physical media, such as, but notlimited to, a compact disc (CD), a digital versatile disc (DVD), afloppy disk, a hard drive, read only memory (ROM), random access memory(RAM), as well as other physical media capable of storing software,and/or combinations thereof.

FIG. 1 is a block diagram of an exemplary network node 100 with fourhosted network interfaces, 104 a, 104 b, 104 c, and 104 d. Though thenetwork node 100 of FIG. 1 is shown with four hosted network interfaces104, in practice a network node may have any number of hosted networkinterfaces. In an exemplary embodiment, the network node 100 may be apiece of communication equipment such as, but not limited to, a switch,a router, a computer, an Optical Cross-connect device, a digitalCross-connect device, or other network equipment capable of receivingand transmitting packets in a connection oriented network thatpre-calculate paths based on priorities of data traffic.

Each network interface of a network node may be coupled to a networklink. The network links may connect the network node to other networknodes in a network. A network node with multiple hosted networkinterfaces that are coupled to multiple network links may receivepackets on a first network interface and direct the packets to anothernetwork interface for transmission. Link/node protection may beimplemented in the network, such that, if the transmission of thepackets through the second network interface is unsuccessful, thenetwork node may re-direct the packets that would be transmitted by thesecond network interface to a third network interface for transmission.

Referring to FIG. 1, the network node 100 has a control component 102.The control component 102 may comprise hardware (e.g., processors,memories, hard drives, disk storages), software (e.g., programs,databases), and any combination thereof. The network interfaces 104 a,104 b, 104 c, and 104 d may be coupled to trunks (not shown),respectively. The control component 102 may direct packets received froma first network interface 104 a to a second network interface 104 b fortransmission. The packets may be data traffic on a primary path. If thesecond network interface 104 b fails to transmit the packetssuccessfully (e.g., network interface 104 b itself fails, the trunkcoupled to network interface 104 b fails, or the down stream networknode fails), the control component 102 may re-direct the packets to betransmitted by the third network interface 104 c or the fourth networkinterface 104 d. The re-direction may be pre-determined, such that thetrunk coupled to the third network interface 104 c or the fourth networkinterface 104 d may be designated as a backup trunk (e.g., alternatetrunk) for the trunk coupled to the second network interface 104 bbefore the transmission failure occurs. In the event of a failure on aprimary path, the data traffic may be re-routed to a bypass tunnel.Thus, the network node 100 may implement a link/node protection schemethat designates a second trunk to carry an alternative path (e.g., abypass tunnel) for a primary path carried on a first trunk.

There may be a plurality of primary paths carried on the first trunk.One or more alternate trunks may be needed to carry corresponding bypasstunnels. The first trunk that carries the primary paths may be referredto as a protected trunk. The designation of an alternate trunk to carrythe corresponding bypass tunnel may be referred to as placing orbuilding a bypass tunnel on the alternate trunk.

The control component 102 may identify a trunk to be protected, andplace bypass tunnels on alternate trunks for each primary path on theprotected trunk. For example, the control component 102 may identify thenetwork link coupled to the network interface 104 b to be a protectedtrunk and the network links coupled to network interfaces 104 c, 104 dto be alternate trunks. Thus, the control component 102 may placecorresponding bypass tunnels on network links coupled to the networkinterfaces 104 c, 104 d for primary paths going through the networkinterface 104 b.

FIG. 2 is a schematic diagram of a trunk protected by multiple Next Hoptrunks according to an exemplary embodiment. As shown, a network 200 mayhave a source node R1 and a destination node R4. Multiple primary pathsbetween nodes R1 and R4 may go through a trunk 202, which is betweennodes R2 and R3. The trunk 202 may be referred to as a protected trunk.To protect the trunk 202, the network 200 may be configured to find allavailable Next Hop trunks for the protected trunk 202 and placecorresponding bypass tunnels on the available Next Hop trunks for allprimary paths on the protected trunk 202. The placement of bypasstunnels may be calculated at a designated server of the network or maybe performed by one or more nodes, e.g., node R2. For example, a firstNext Hop trunk (e.g., Next Hop trunk 204) and a second Next Hop trunk(e.g., Next Hop trunk 206) may be identified as the available Next Hoptrunks. The Next Hop trunk 204 may pass through node R5 and the Next Hoptrunk 206 may pass through node R6. Node R3 may build a bypass tunnel onNext Hop trunk 204 and/or Next Hop trunk 206 for each primary path onprotected trunk 202 respectively. The protected trunk 202 may be a highbandwidth trunk and the available Next Hop trunks 202, 204 may be lowbandwidth trunks.

The link/node protection scheme may start by determining the physicalbandwidth of each primary path on the protected trunk. Referring to FIG.2, node R3 may determine the physical bandwidths of each primary path onthe protected trunk 202 using the overbooking factors. For example, aprimary path may have an overbooking factor of four-hundred percent(400%). If the logical bandwidth of the path is four hundred (400) kbps,the physical bandwidth of the path is one hundred (100) kbps. Thephysical bandwidths for each primary path are the demands that may beplaced on the available Next Hop trunks.

The corresponding bypass tunnels for the primary paths may beestablished on a one-by-one basis using a predetermined order, e.g., adescending order of the setup priority of each primary path. For pathswith the same setup priorities, bypass tunnels may be established usinga predetermined order, e.g., a descending order of the physicalbandwidth of the primary path. For example, in the network 200, theremay be four primary paths: Paths A, B, C and D carried on the protectedtrunk 202. Path A may have a setup priority of seven (7), Path B mayhave a setup priority of five (5), Path C may have a setup priority offive (5), and Path D may have a setup priority of zero (0). Path C mayhave a larger physical bandwidth than Path B. Node R3 may build bypasstunnels for each primary path in a descending order of setup priority.Therefore the link/node protection scheme may build bypass tunnels forPath A first, then Path C, then Path B, then Path D.

After the selection of a primary path, an alternate trunk for the bypasstunnel may be selected. The alternate trunk may be selected from aplurality of available Next Hop trunks. The selection of the alternatetrunk may start with a constraint-based trunk-selection algorithm suchas, but not limited to, Constraint-based Shortest Path First (CSPF). TheCSPF algorithm may apply constraints first and then a cost matrix. Theselection of a Next Hop trunk for a specific path may apply existingconstraints and an existing cost matrix. For example, the CSPF algorithmmay start with administrative group settings constraint. The CSPFalgorithm may also apply other constraints, such as, but not limited to,administrative cost, CSPF area settings, and explicit routeinstructions.

The administrative group settings constraint may also be referred to as“coloring” or “matching of color.” Each trunk in a network may have aspecific color (e.g., red, blue, or yellow) specified by a networkadministrator. The network administrator may also establish a color(e.g., red, blue, or yellow) for each primary path of the network. Whena primary path may be set up, the color of trunks associated with theprimary path may be required to conform to a color requirement of theprimary path. For example, a red primary path may only be placed on blueor red trunks. The network administrator may also establish a color(e.g., red, blue, or yellow) for each bypass tunnel in the network. Thecolor of each bypass tunnel may be set to match the color of thecorresponding primary path. Alternately, a bypass tunnel may have acolor different from the color of the corresponding primary path. Thecolor of each bypass tunnel may be set one-by-one or universally (e.g.,the network administrator may use a global setting of the network). The“coloring” of primary paths is well known. When placing bypass tunnels,the “coloring” of bypass tunnels may follow the “coloring” of primarypaths.

After applying the constraints, the CSPF algorithm may apply a costmatrix. Cost matrixes are well known. If the CSPF costs are equal, thetrunk selection may follow a predetermined order, e.g., a descendingorder of the priority bandwidth of the trunks for the bypass tunnel'ssetup priority.

If a primary path on the protected trunk being considered for a bypasstunnel is larger than the priority bandwidth on any of the availableNext Hop trunks, a bypass tunnel for that primary path may not be built.The operation of building bypass tunnels may move to the next primarypath, and network operators may be notified of the failure of building abypass tunnel for that particular primary path. For example, a primarypath on protected trunk 202 has a physical bandwidth of ten (10) Gbpsand a setup priority of five (5). The priority bandwidth for a holdingpriority of five (5) may be eight (8) Gbps on the Next Hot trunks 204and may be six (6) Gbps on the Next Hop trunk 206. A bypass tunnel forthe primary path could not be built. The operation of building bypasstunnels may move to the next primary path on the protected trunk 202 anda network administrator may be notified of the failure.

A network administrator may set a threshold for availability of a NextHop trunk for each holding priority value. That is, the networkadministrator may determine that a Next Hop trunk may be taken out of apool of available Next Hop trunks when the available physical bandwidthfor a given holding priority value on the Next Hop trunk reaches aspecified level. The specified level may be user configurable andadjustable. For example, when the priority bandwidth on the Next Hoptrunk 204 becomes less than or equal to twenty-percent (20%) of thephysical bandwidth for a holding priority value of five (5), the NextHop trunk 204 may be moved into a standby status when building bypasstunnels for primary paths with a setup priority value of five (5). Thatis, no additional bypass tunnels may be built on the Next Hop trunk 204for primary paths of setup priority value of five (5) unless the NextHop trunk 206 also reaches the standby status for the holding priorityvalue of five (5). In that case, all alternate trunks in standby statusmay become active again, and the priority bandwidths on the alternatetrunks may be re-calculated. Bypass tunnels may then be placed upon theNext Hop trunk 204 and the Next Hop trunk 206 according to a newdescending sequence of the priority bandwidth.

When each bypass tunnel is placed, no physical bandwidth may be reservedon the Next Hop trunk accommodating the bypass tunnel. Upon completionof placing corresponding bypass tunnels for each primary path of theprotected trunk, the reserved physical bandwidth for the correspondingbypass tunnels on the Next Hop trunks may be set to a specified value(e.g., zero) by a network administrator. Alternately, the reservedphysical bandwidth for the corresponding bypass tunnels may be set byadjusting the physical bandwidth of the primary path of the bypasstunnel by a bypass tunnel overbooking factor. A network administratormay set the bypass tunnel overbooking factor on a trunk-by-trunk basisor universally.

A specified low value (e.g., zero (0)) of the reserved physicalbandwidth for the bypass tunnel or a low bypass tunnel overbookingfactor (e.g., zero (0)) may be set. Because bypass tunnels may not carryany data traffic before a link failure occurs on the primary path, theavailable physical bandwidth may be reserved for other primary paths orbypass tunnels by setting a low value of the reserved physical bandwidthfor the bypass tunnel or a low bypass tunnel overbooking factor. Forexample, a primary path on the protected trunk 202 may have a logicalbandwidth of four hundred (400) kbps, an overbooking factor of four (4)and a physical bandwidth of one hundred (100) kbps. A bypass tunnel forthe primary path may be placed on the Next Hop trunk 204 with a reservedphysical bandwidth being set directly to a low value, e.g., ten (10)kbps or zero (0). Alternately, the reserved physical bandwidth may beset by adjusting the primary path's physical bandwidth by a bypasstunnel overbooking factor such as, but not limited to ten-percent (10%)or zero (0). If the reserved physical bandwidth of the bypass tunnel isset to zero (0) or the bypass tunnel overbooking factor on the Next Hoptrunk 204 is set at zero (0), the bypass tunnel will not reservephysical bandwidth on the Next Hop trunk 204. If the reserved physicalbandwidth of the bypass tunnel is set to ten (10) kbps, or a bypasstunnel overbooking factor is set at ten-percent (10%), the bypass tunnelwill reserve ten (10) kbps bandwidth on the Next Hop trunk 204. Whetherthe reserved physical bandwidth is ten (10) kbps or zero (0), the datatraffic on the bypass tunnel may not be impacted, because the bypasstunnel still has a provisioned bandwidth of one hundred (100) kbps. Thatis, from the perspective of the data traffic carried on a primary pathor a bypass tunnel, the bandwidth is the full logical bandwidth.

In the event that the bypass tunnel overbooking factor is set to anon-zero value, the combined physical bandwidths of the bypass tunnelsand the existing primary paths on the Next Hop trunk may exceed thephysical bandwidth of the Next Hop trunk. The link/node protectionscheme may use a preemption algorithm as known in the art. For example,the protected trunk 202 may have a primary path that has a physicalbandwidth of one hundred (100) Gbps, a setup priority of five (5), and aholding priority of five (5). A bypass tunnel for the primary path maybe placed on the Next Hop trunk 204. The priority bandwidth for holdingpriority five (5) may be fifteen (15) Gbps on the Next Hop trunk 204.The Next Hop trunk 204 may have a ten-percent (10%) overbooking factorfor bypass tunnels. After placing all corresponding bypass tunnels foreach of primary paths on the protected trunk 202, the one hundred (100)Gbps physical bandwidth primary path may reserve ten (10) Gbps physicalbandwidth for the bypass tunnel. But the Next Hop trunk 204 may haveonly five (5) Gbps physical bandwidth left because existing primarypaths on the Next Hop trunk 204 with holding priorities less than five(5) may have used ten (10) Gbps physical bandwidth. The bypass tunnelmay preempt one or more existing primary paths or one or more bypasstunnels with holding priorities lower than five (5) on the Next Hoptrunk 204 to reserve the ten (10) Gbps physical bandwidth on the NextHop trunk 204.

The bypass tunnels may be established when primary paths are first setup. The bypass tunnels may then go into hibernation or standby modeuntil they are triggered by a failure of the protected trunk. Forexample, a failure may be detected by Loss Of Signal (LOS) as defined inFRR specifications, and all traffic may then be routed from the primarypaths onto the corresponding bypass tunnels. Referring back to FIG. 2,all primary paths on the protected trunk 202 may be bundled with allbypass tunnels on the Next Hop trunks 204, 206. That is, all primarypaths on the protected trunk 202 may be associated with correspondingbypass tunnels on the Next Hop trunks 204, 206. The associationinformation may be maintained in the control component 102 on node R3.Upon detection of the LOS on a primary path on the protected trunk 202,all data traffic for all primary paths on the protected trunk 202 may bere-routed to bypass tunnels on the Next Hop trunks 204, 206. Typically,this re-routing occurs quickly, e.g., within fifty milliseconds (50 ms).

The operation of building bypass tunnels for primary paths on aprotected trunk may be carried out periodically. A network administratormay trigger the operation or pre-schedule the operation. The networkbypass tunnels may be updated by using the latest network resourcesparameters. For example, the network 200 may schedule periodic bypasstunnel building for all primary paths on the protected trunk 202 toprovide link protection for the protected trunk 202.

FIG. 3 is a schematic diagram of a link/node protected by multiple NextNext Hop trunks according to an exemplary embodiment. The abovedescribed Next Hop link/node protection may also be applied to a NextNext Hop protection scheme. As shown in FIG. 3, a network 300 may have asource node R1 and a destination node R5. A trunk 302 between nodes R2and R4 may comprise node R3. To protect node R3 and the trunk 302, afirst Next Next Hop trunk (e.g., Next Next Hop trunk 306) and a secondNext Next Hop trunk (e.g., Next Next Hop trunk 308) may be used toestablish bypass tunnels for all primary paths carried on the trunk 302.The Next Next Hop trunk 306 may pass through nodes R6 and R7. The NextNext Hop trunk 308 may pass through nodes R8 and R9. The establishmentof bypass tunnels for each primary path using the Next Next Hop trunksmay apply the operation described above for Next Hop trunks in a similarmanner.

FIG. 4 is a flow diagram of a method to implement link/node protectionaccording to an exemplary embodiment. Method 400 may start at block 402.In block 402, a node in a network may compute the physical bandwidth foreach primary path carried on a protected trunk and the prioritybandwidth for each available alternate trunk. Typically, the nodehandling the computation may be an immediate upstream node of theprotected trunk (e.g., the node immediately before the protected trunkalong the data traffic path). The immediate upstream node may implementthe link/node protection. The physical bandwidth for a primary path maybe computed by dividing the logical bandwidth of the primary path by theoverbooking factor of the primary path. A priority bandwidth for aholding priority of an available alternate trunk may be calculated asdescribed previously. For example, in network 200, a protected trunk 202starts from a network interface of an immediate upstream node R2. NodeR2 may implement the link/node protection to protect the protected trunk202. Available Next Hop trunks may be the Next Hop trunk 204 and theNext Hop trunk 206. Node R2 may compute the physical bandwidth for eachprimary path carried on the protected trunk 202. Node R2 may alsocompute the priority bandwidth for each holding priority of theavailable Next Hop trunks 204, 206. The method 400 may continue to block404.

In block 404, the immediate upstream node may select each primary pathon the protected trunk for which to place bypass tunnels on availablealternate trunks, respectively, wherein each path is considered based ona prescribed order. For example, node R2 of network 200 may select eachprimary path on the protected trunk 202 to place bypass tunnels on theNext Hop trunks 204, 206. Each primary path on the protect trunk 202 maybe considered in a descending order of setup priority. For primary pathswith the same setup priority, each primary path may be considered in adescending order of physical bandwidth. The method 400 may continue toblock 406.

In block 406, the immediate upstream node may select an alternate trunkto place the bypass tunnel using a trunk selection scheme. The trunkselection scheme may comprise selecting available alternate trunks basedon a constraint-based trunk-selection algorithm, considering availablealternate trunks in a prescribed order of priority bandwidth, notifyingthe network administrator if the largest priority bandwidth is less thanthe physical bandwidth of the primary path considered before moving toplace bypass tunnel for the next primary path, enforcing a userspecified threshold value of a priority bandwidth for an availablealternate trunk to enter into a standby status and reactivate theavailable alternate trunk when all available alternate trunks enter intothe standby status. For example, Node R3 may implement the trunkselection scheme that select available alternate trunks based on aConstraint-based Shortest Path First algorithm. Then, the Next Hoptrunks 204, 206 may be considered in a descending order of prioritybandwidth for the corresponding setup priority of the primary path beingconsidered. A network administrator of network 200 may be notified ifthe largest priority bandwidth for the corresponding setup priority isless than the physical bandwidth of the primary path considered. Thenetwork administrator may take action to improve the design of thenetwork (e.g., adding a new trunk to balance the data traffic loads).Node R3 may also enforce a user specified threshold value, e.g.,twenty-percent (20%) of total physical bandwidth. That is, when apriority bandwidth of Next Hop trunk 204, or Next Hop trunk 206 may beequal to or less than twenty-percent (20%) of the total physicalbandwidth, the Next Hop trunk may be put into a standby status and maynot be assigned any additional bypass tunnels until all available NextHop trunks enter the standby status. When all available Next Hop trunksare in standby status, then the standby Next Hop trunks may becomeactive again, and the priority bandwidth on the available Next Hoptrunks are calculated again. Bypass tunnels may then be placed upon theavailable Next Hop trunks according to a new descending order of thepriority bandwidth. The twenty-percent (20%) may be configured andadjusted by the network administrator. The method 400 may continue toblock 408.

In block 408, the immediate upstream node may set the reserved physicalbandwidth of all bypass tunnels on the alternate trunks to a specifiedvalue. The immediate upstream node may perform preemption if thecombined reserved physical bandwidth of bypass tunnels and physicalbandwidth of existing primary paths on an alternate trunk exceeds thephysical bandwidth of the alternate trunk. The specified value may be auser defined value or determined by a bypass overbooking factor on thealternate trunks. The physical bandwidth for a bypass tunnel may bedetermined after all the bypass tunnels have been placed for a protectedtrunk. The physical bandwidths of a bypass tunnel may be set to a userdefined value such as, but not limited to, zero (0). Alternately, thephysical bandwidth of the bypass tunnel may set by applying a bypassoverbooking factor (e.g., ten-percent (10%)) to the physical bandwidthof the corresponding primary path. This setting may reserve networkresources because the bypass tunnels may not be used before there is alink failure for the protected trunk. By setting the bypass overbookingfactor to a value less than one-hundred percent (100%), the alternatetrunks may accommodate more bypass tunnels or carry more primary paths.The user defined physical bandwidth value for the bypass tunnel andbypass overbooking factor may be set by a network administrator for aspecific protected trunk or universally for every protected trunk.

For example, a primary path on the protected trunk 202 may have aphysical bandwidth of two hundred (200) kbps. Node R2 may place a bypasstunnel on the Next Hop trunk 204 for the primary path. Node R2 mayspecify a user defined physical bandwidth value for the bypass tunnel(e.g., two hundred (200) kbps) or apply a bypass tunnel overbookingfactor of one-hundred percent (100%). In either case, two hundred (200)kbps may be reserved for this bypass tunnel. Available bandwidth on theNext Hop trunk 204 may decrease accordingly although the two hundred(200) kbps may not be used before a failure occurs on the protectedtrunk 202. A network administrator may define the value for the physicalbandwidth of the bypass tunnel to be twenty (20) kbps, or apply a bypasstunnel overbooking factor of ten-percent (10%) to the physical bandwidthof the corresponding primary path. Either way, the bypass tunnel mayonly reserve twenty (20) kbps and does not reserve the additional onehundred and eighty (180) kbps. The bypass overbooking factor may be setto zero (0) if the network administrator decides not to reservebandwidth for bypass tunnels.

By setting a non-zero value for the physical bandwidth of bypass tunnelor applying a non-zero bypass tunnel overbooking factor, preemption mayoccur. When the physical bandwidth of a bypass tunnel is not zero, thecombined reserved physical bandwidth of bypass tunnels and physicalbandwidth of existing primary paths on the alternate paths may exceedthe physical bandwidth of the alternate trunk. The bypass tunnels withhigher setup priorities may preempt bypass tunnels with lower holdingpriorities or existing primary paths with lower holding priorities as iswell known. The method 400 may continue to block 410.

In block 410, the immediate upstream node may associate all primarypaths on the protected trunk with all corresponding bypass tunnels. Allprimary paths on the protected trunk and their corresponding bypasstunnels on the Next Hop trunks may be “bundled” together, so thatre-routing can occur at about the same time. For example, after allbypass tunnels have been established for all primary paths on theprotected trunk 202, node R3 may associate all primary paths on theprotected trunk 202 and their corresponding bypass tunnels placed on theNext Hop trunks 204, 206. So if a failure is detected for any primarypaths on the protected trunk 202, all data traffic of all primary pathson the protected trunk 202 may be re-routed to corresponding bypasstunnels on the Next Hop trunks 204, 206. The method 400 may end.

The method 400 may also be applied to protect a network node. To protecta network node, the method 400 may be applied to place bypass tunnels onNext Next Hop trunks. An immediate upstream node may perform the stepsof method 400 to protect a trunk and the immediate upstream node of thetrunk. The steps of method 400 may be performed to place bypass tunnelsfor each of the primary paths on the protected trunk on Next Next Hoptrunks in a similar manner.

Thus, the network nodes may implement link/node protection by placingbypass tunnels among available alternate trunks. The link/nodeprotection may be implemented in a MPLS Traffic Engineering enabledenvironment and any other network environment that pre-calculates a pathand assigns a setup priority and a holding priority. The link/nodeprotection may provide link protection under Next Hop protection scheme,e.g., link protection. The link/node protection may also providelink/node protection under Next Next Hop protection scheme, e.g., nodeprotection. The link/protection may protect a high bandwidth trunk byusing bypass tunnels on multiple low bandwidth trunks. Thelink/protection may be applied to a specific link/node or may be appliedfor all links/nodes of a network. Further, the link/node protection maybe implemented to establish bypass tunnels when the primary paths areset up or periodically to account for changing conditions.

In the preceding specification, various exemplary embodiments have beendescribed with reference to the accompanying drawings. It will, however,be evident that various modifications and changes may be made thereto,and additional embodiments may be implemented, without departing fromthe broader scope of the invention as set forth in the claims thatfollow. The specification and drawings are accordingly to be regarded inan illustrative rather than restrictive sense.

1. A method comprising: selecting a primary path on a first trunk forwhich to place a corresponding bypass tunnel on an alternate trunk;selecting one or more alternate trunks using a constraint-basedtrunk-selection algorithm; determining if at least one of the selectedalternate trunks has sufficient priority bandwidth, wherein the prioritybandwidth of each selected alternate trunk is the total bandwidth of theselected alternate trunk minus the physical bandwidth allocated to allexisting primary paths on the selected alternate trunk with equal orhigher holding priority values; in the event that the physical bandwidthof the primary path is larger than the priority bandwidth of eachalternate trunk, notifying a network administrator; in the event thatone or more alternate trunks have priority bandwidths larger than thephysical bandwidth of the primary path, selecting an alternate trunkfrom the one or more alternate trunks having priority bandwidths largerthan the physical bandwidth of the primary path based on apre-determined order of priority bandwidth; comparing the prioritybandwidth of the selected alternate trunk to a threshold value; in theevent that the priority bandwidth of the selected alternate trunk is notgreater than the threshold value, placing the selected alternate trunkin a standby status; and in the event that the priority bandwidth of theselected alternate trunk is greater than the threshold value, placingthe bypass tunnel on the selected alternate trunk and setting a reservedphysical bandwidth for the corresponding bypass tunnel on the selectedalternate trunk.
 2. The method of claim 1, further comprising selectingeach primary path on the first trunk to place a corresponding bypasstunnel.
 3. The method of claim 1, further comprising re-activating allalternate trunks in the standby status in the event that all of thealternate trunks enter standby status.
 4. The method of claim 1, whereinthe reserved physical bandwidth is set to a user specified value.
 5. Themethod of claim 1, wherein the reserved physical bandwidth is set usinga bypass overbooking factor.
 6. The method of claim 1, furthercomprising preempting one or more existing primary paths or one or morebypass tunnels on the alternate trunk in the event that the bandwidth ofall existing primary paths and bypass tunnels exceeds the physicalbandwidth of the alternate trunk.
 7. The method of claim 2, furthercomprising re-routing primary paths to their corresponding bypasstunnels within a specified time in response to the first trunk failing.8. The method of claim 1, wherein the primary path is a Label SwitchedPath (LSP) in a MPLS Traffic Engineering enabled network.
 9. The methodof claim 1, wherein the physical bandwidth of the primary path is alogical bandwidth of the primary path divided by an overbooking factorof the primary path.
 10. The method of claim 1, wherein the first trunkis a direct physical link and the one or more alternate trunks are NextHop trunks.
 11. The method of claim 1, wherein the first trunk is aphysical link comprising a node and the one or more alternate trunks areNext Next Hop trunks.
 12. The method of claim 1, wherein theconstraint-based trunk-selection algorithm is a Constraint-basedShortest Path First (CSPF) algorithm.
 13. The method of claim 12,wherein the Constraint-based Shortest Path First (CSPF) algorithmcomprises constraints of: administrative cost, administrative groupsettings, CSPF area settings, and explicit route instructions.
 14. Themethod of claim 1, wherein the first trunk is a high bandwidth trunk andthe one or more alternate trunks are low bandwidth trunks.
 15. Anon-transitory computer readable media comprising code to perform theacts of the method of claim
 1. 16. A network node comprising: a controlcomponent comprising one or more processors, the control componentconfigured to: select a primary path on a first trunk for which to placea corresponding bypass tunnel on an alternate trunk; select one or morealternate trunks using a constraint-based trunk-selection algorithm;determine if at least one of the selected alternate trunks hassufficient priority bandwidth, wherein the priority bandwidth of eachselected alternate trunk is the total bandwidth of the selectedalternate trunk minus the physical bandwidth allocated to all existingprimary paths on the selected alternate trunk with equal or higherholding priority values; in the event that the physical bandwidth of theprimary path is larger than the priority bandwidth of each alternatetrunk, notify a network administrator; in the event that one or morealternate trunks have priority bandwidths larger than the physicalbandwidth of the primary path, select an alternate trunk from the one ormore alternate trunks having priority bandwidths larger than thephysical bandwidth of the primary path based on a pre-determined orderof priority bandwidth; compare the priority bandwidth of the selectedalternate trunk to a threshold value; in the event that the prioritybandwidth of the selected alternate trunk is not greater than thethreshold value, place the selected alternate trunk in a standby status;and in the event that the priority bandwidth of the selected alternatetrunk is greater than the threshold value, place the bypass tunnel onthe selected alternate trunk and set a reserved physical bandwidth forthe corresponding bypass tunnel on the selected alternate trunk; and atleast one network interface.
 17. The network node of claim 16, furtherconfigured to associate all primary paths and their corresponding bypasstunnels and re-route all primary paths to their corresponding bypasstunnels within a specified time in response to the first trunk failing.18. The network node of claim 16, wherein the first trunk is a directlink.
 19. The network node of claim 16, wherein the one or morealternate trunks are Next Hop trunks.
 20. The network node of claim 16,wherein the one or more alternate trunks are Next Next Hop trunks.